Graphene applications on flexible substrates have advantages in photonics, optoelectronics and organic electronics such as in light-emitting diodes and touch screen technology due to their unique electrical, mechanical, optical and thermal properties. Excellent electrical conductivity, thermal conductivity, and chemical resistance make graphene a perfect material for replacing copper as circuits. Massive flexible graphene circuit manufacturing can be achieved by transferring graphene onto flexible substrates and performing plasma etching afterwards. Chemical Vapor Deposition (CVD) graphene can be transferred onto flexible substrates as good quality raw material for patterning circuits. It is proved that CVD graphene has good adhesion on commonly used base films PI and LCP, which allows the possibility of manufacturing graphene circuits by oxygen plasma etching.
A conventional transfer method includes the following steps of: grow CVD graphene on a metal foil, usually copper; covering a thermo-releasable material on the graphene film, followed by pressing and peeling off the thermo-releasable material on the graphene film so as to attach the graphene film thereon; and covering the thermo-releasable material together with the graphene film on the planar surface of the object, followed by heating so as to directly attach the graphene film onto the planar surface of the object; and modifying the graphene surface by plasma etching to form circuits is performed using reel to reel format afterwards.
Compared to conventional copper circuits, graphene circuits on PI, LCP and COP offer significantly improved electrical conductivity, thermal conductivity and chemical resistance. U.S. Pat. No. 8,241,992 (Clevenger et al), U.S. Pat. No. 9,012,882 (Duan et al), and U.S. Pat. No. 9,087,692 (Accardi et al) teach graphene patterning methods.